The interaction between the soil and the atmosphere greatly contributes to the climate system characterization. In particular, rainfall and temperature are major variables in determining the hydric condition (SH) of the soil. In this work we analyzed the hydric response of soil to the variability of the Monthly Accumulated Precipitation and Potential Evapotranspiration in eastern rainfed region of Argentina. While the increase in rainfall observed in recent years favor summer crops (for greater input of water in the system), the imbalance between Precipitation and Potential Evapotranspiration gives evidence that this situation can not satisfy all their requirements. In addition, the greater variability observed during the warm semester until April, highlights the vulnerability in agricultural planning for those months. Excess hydric conditions predominate eastward during the cold semester (April -September) and deficit hydric conditions predominate westward during the warm semester (October-March). The transition zone is characterized by high seasonality, with similar behavior as eastern during warm months and western during cold months, in terms of excess variability. The variety of factors affecting water availability and their variability, determine the complexity of the soil-atmosphere system, in which precipitation is the most important contribution to the water in soil.

Keywords: hydric condition (SH) – climate variability- rainfed region